Noisy Amcoraire ductless mini split AC

I've got a noisy Amcoraire ductless mini split AC. I posted a video of the AC on youtube (see link below). In the video you can see that there is one spot that makes more noise when depressed, and less noise when pulled away from the AC. I shoved some wads of duct tape behind that point (and removed them for this video) but it isn't a good long term solution. The noise is worst when the humidity is high.

Any ideas about how to fix it? I'm considering removing the fins in front of the fan and holding some sandpaper against the fan while it is running to mill it down, but I'm not sure if that is a good idea.

Thanks

https://youtu.be/nsI5LuiR7uo